EP0044431A1 - Appareil pour détecter les variations locales de température d'un objet et les endroits des variations de température - Google Patents

Appareil pour détecter les variations locales de température d'un objet et les endroits des variations de température Download PDF

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Publication number
EP0044431A1
EP0044431A1 EP19810104858 EP81104858A EP0044431A1 EP 0044431 A1 EP0044431 A1 EP 0044431A1 EP 19810104858 EP19810104858 EP 19810104858 EP 81104858 A EP81104858 A EP 81104858A EP 0044431 A1 EP0044431 A1 EP 0044431A1
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EP
European Patent Office
Prior art keywords
temperature
sensing element
magnetic material
band
shaped magnetic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP19810104858
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German (de)
English (en)
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EP0044431B1 (fr
Inventor
Yasushi Wakahara
Hirokazu Sato
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toshiba Corp
Original Assignee
Toshiba Corp
Tokyo Shibaura Electric Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP8490580A external-priority patent/JPS5710431A/ja
Priority claimed from JP8490280A external-priority patent/JPS5710430A/ja
Priority claimed from JP55129460A external-priority patent/JPS592852B2/ja
Priority claimed from JP13284380A external-priority patent/JPS5759128A/ja
Application filed by Toshiba Corp, Tokyo Shibaura Electric Co Ltd filed Critical Toshiba Corp
Publication of EP0044431A1 publication Critical patent/EP0044431A1/fr
Application granted granted Critical
Publication of EP0044431B1 publication Critical patent/EP0044431B1/fr
Expired legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K3/00—Thermometers giving results other than momentary value of temperature
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/36—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using magnetic elements, e.g. magnets, coils
    • G01K7/38—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using magnetic elements, e.g. magnets, coils the variations of temperature influencing the magnetic permeability

Definitions

  • This invention relates to an apparatus for detecting the local temperature variations of an object and the sites of the temperature variations.
  • a temperature variation-site detecting apparatus which detects abnormal temperatures occurring, for example, in an elongate pipe on a tank or the leakage of a hot or cold liquid and the sites of all these accidents by utilizing changes with time in the characteristic impedance of a temperature variation-detecting cable comprising a magnetic material disposed between a pair of conductors.
  • Fig. 1 is a schematic diagram of an example of a prior art temperature variation-site detecting apparatus.
  • a temperature variation-detecting calbe 32 is mounted on part of the outer peripheral wall of an object 30, for example, a tank.
  • the cable 32 is, as shown in Fig. 2, of the concentric type which comprises a linear core conductor 34, outer hollow cylindrical conductor 36 surrounding the core conductor 34 and a magnetic material 38 which has a retatively low Curie temperature and is filled between the outer conductor 36 and core conductor 34.
  • the magnetic material 38 is formed by mixing ferrite powder with, for example, an insulating adhesive. This magnetic material 38 is chosen to have such a Curie temperature as is set at the upper or lower limit of a temperature range regarded as, for example, an abnormal level.
  • the starting end of the cable 32 in connected to a pulse generator 40 and pulse time difference detector 42.
  • the terminal end of the cable 32 is short-circuited or may be left open.
  • the pulse generator 40 Upon receipt of a set signal, the pulse generator 40 sends forth a short width pulse signal to the starting end of the cable 32.
  • the pulse time difference detector 42 counts a difference between a point of time at which the output pulse signal is received and a point of time at which the pulse signal is reflected from the prescribed spot of the cable 32.
  • a signal denoting the time difference is conducted to a detector 44 for indicating a site at which temperature variations take place (hereinafter referred to as "a temperature variation site detector).
  • This temperature variation site detector 44 determines the occurrence or absence of abnormal temperature and the site of the abnormal temperature from the above-mentioned time difference thus detected.
  • a pulse signal emitted from the pulse generator 40 is supplied to the starting end of the cable 32, and then conducted through the cable 32. Where, at this time, a substantially fixed temperature prevails over the whole of the object 30, then the impedance of the cable 32 also remains fixed over the whole of the object 30. Therefore, the output pulse signal is reflected only at the terminal end of the cable 32.
  • the character l denotes the total length of the cable 32, and the character V represents the speed at which a pulse signal is transmitted through the cable.
  • the character l 1 is a distance from the starting end of the cable 32 to point Q l .
  • T 1 , T 2 T 1 ⁇ T 0 , T 2 ⁇ TO
  • the temperature variation site detector 44 judges that an abnormal temperature arises in the object 30, and determines the site and range of the abnormal temperature.
  • the aforementioned prior art temperature variation-site detecting apparatus indeed has the advantages that it is possible to easily detect the occurrence of abnormal temperatures in an object, for example, a tank, and the sites of the abnormal temperatures; and sites of abnormal temperatures can be detected over a broad area of the object 30, thereby making it possible to easily determine sites of abnormal temperatures even in a large object.
  • the cable 32 is constructed by uniformly filling a magnetic material 38 in a space defined between the core conductor 34 and outer hollow cylindrical conductor 36.
  • the conventional process comprises mixing ferrite powder with an adhesive, and filling the mixture between the conductors 34, 36 or applying ferrite powder on the outer peripheral wall of the core conductor 34 by means of a rubber type adhesive. Consequently this conventional apparatus has the drawbacks that a time-consuming process is invalved of previously crushing ferrite into powder and then uniformly mixing the powder with the adhesive, thus undesirably leading to an increase in the cost of producing the cable 34 and consequently a temperature variation-site detecting apparatus.
  • the ferrite powder contained in the magnetic material 38 rather tends to give rise to the formation of a diamagnetic field, reducing the permeability of the magnetic member 38. Therefore, a decline appears in the changes of the inductance of the cable 32 resulting from temperature variations near the prescribed Cuire temperature of the magnetic material 38, and consequently in the sensitivity with which the temperature variation-site detecting apparatus detects temperature variations.
  • this invention provides an apparatus for detecting the local temperature variations of an object and the sites of the temperature variations which comprises at least one temperature-sensing element constituted by a band-shaped magnetic material having a predetermined Curie temperature; a pulse generator for supplying a pulse signal to at least one end of the temperature-sensing element; a pulse time difference detector for determining a difference between a point of time at which the pulse signal is received and a point of time at which a reflected pulse signal of the pulse signal from a site at which the characteristic impedance of the temperature-sensing element has changed is received; and a temperature variation site detector for determining a site of temperature variation from the above-mentioned time difference.
  • Fig. 4 shows a cable type temperature-sensing element 46 according to one embodiment of this invention.
  • This temperature-sensing element 46 comprises a band-shaped amorphous magnetic material 48 having a Curie temperature corresponding to the lower limit of an anti- ciplated abnormal temperature range and two coiled con- ductors 50, 52 coated with an insulation layer and wound about the band-shaped amorphous magnetic material 48.
  • the amorphous magnetic material 48 is an alloy which mainly consists of a ferromagnetic transition metal such as iron, copper or nickel and has a prominently higher relative permeability than ferrite powder.
  • the amorphous magnetic material 48 is an alloy which mainly consists of a ferromagnetic transition metal such as iron, copper or nickel and has a prominently higher relative permeability than ferrite powder.
  • the temperature-sensing element 46 is, for example, mounted on an object 30 as shown in Fig. 5.
  • the starting end of the temperature-sensing element- 46 is connected to a pulse generator 40 and pulse time difference detector 42.
  • An output signal from the pulse time difference detector 42 is supplied to the temperature variation site detector 44 of a temperature variation-site detecting apparatus 54.
  • the band-shaped magnetic material 48 has the same function as the magnetic material 38 of the prior art temperature sensing element 32 of Fig. 2, and determines temperature variations and the sites of the temperature variations.
  • the band-shaped magnetic material 48 can be easily produced at low cost.
  • the temperature-sensing element 46 is manufactured simply by winding two insulation layer coated-conductors 50, 52 around the band-shaped magnetic material 48 at a few lower cost than the prior art temperature-sensing element 32, thereby making it possible to manufacture a temperature variation-site detecting apparatus 54 at reduced cost.
  • a diamagnetic field formed in the band-shaped amorphous magnetic material 48 is weak, thereby assuring a relative permeability as higher as 100 to 1000 times than that of the prior art magnetic material formed of ferrite powder. Since the band-shaped magnetic material 48 is wound with two conductors 50, 52, the temperature-sensing element 46 has a more increased inductance. Therefore, for more noticeable variations than in the conventional ferrite powder type temperature-sensing element 32 take place in the inductance of the band-shaped magnetic material 48 in the proximity of its Curie temperature, that is, the characteristic impedance of the temperature-sensing element 46. As a result, a pulse signal reflected from a site having an abnormal temperature has a higher level or intensity, thereby prominently elevating the detection sensitivity of the temperature variation-site detecting apparatus 54.
  • the Curie temperature of the amorphous magnetic material 48 can be selected over a considerably broad range depending on the material chosen. Accordingly, the magnetic material 48 offers the advantage that the upper or lower limit of an anticipated abnormal temperature range can be freely predetermined.
  • the amorphous magnetic material 48 is formed of a band-shaped alloy whose permeability is uniformly distributed throughout the temperature-sensing element 46, thereby preventing pulse signals reflected from various sites of the temperature-sensing element 46 from being unbalanced in intensity, and consequently ele- "vating the efficiency of the temperature-sensing element 46.
  • amorphous magnetic material 48 having a strong alloyed structure With the amorphous magnetic material 48 having a strong alloyed structure, atoms constituting the magnetic material 48 little tend to present rearrangement during the application of the magnetic material 48, thereby reducing the possibility of the relative permeability of the temperature-sensing element 46 being changed during its application.
  • Fig. 6 shows a temperature-sensing element 46 according to a second embodiment of the invention.
  • This temperature-sensing element 46 also comprises a band-shaped magnetic material 48 having a prescribed Curie temperature and two conductors 50, 52.
  • one conductor 52 is wound about the band-shaped magnetic material 48 from end to end, whereas the other conductor 50 extends along one lateral side of the band-shaped magnetic material 48.
  • the temperature-sensing element 46 according to the second embodiment still has the same effect as that of the first embodiment.
  • Fig. 7 indicates a temperature-sensing element 46 according to a third embodiment of the invention.
  • the parts the same as those of Figs. 4 and 5 are denoted by the same numerals, description thereof being omitted.
  • the temperature-sensing element 46 according to the third embodiment comprises a. band-shaped magnetic material 48 and two conductors 50, 52 which are wound about the band-shaped magnetic member 48 along its axis at a predetermined interval in a prescribed number of turns for each interval.
  • Fig. 8 sets forth a temperature-sensing element 46 according to a fourth embodiment of this invention, which is constructecd by winding two conductors 50, 52 respectively about two parallel extending band-shaped magnetic materials 48, 49.
  • Fig. 9 illustrates a temperature-sensing element 46 according to a fifth embodiment of this invention, which is constructed by winding two conductors 50, 52 respectively about two parallel extending arms of a U-shaped magnetic material 48 bent at the center 55.
  • Fig. 10 indicates a temperature-sensing element 46 according to a sixth embodiment of this invention, which is constructed by winding a conductor 52 coated with an insulation layer about a band-shaped amorphous magnetic material 48.
  • the band-shaped magnetic material 48 constitutes a pulse signal-transmitting circuit.
  • the conductive amorphous magnetic material 48 which concurrently acts as a conductor and magnet simplifies the construction of the temperature-sensing element 46.
  • Fig. 11 shows a temperature-sensing element 46 according to a seventh embodiment of this invention, which is constructed by winding a conductor 52 about a band-shaped magnetic material 48 constituting a pulse signal-transmitting circuit along the axis of the magne- ' tic material 48 at a predetermined interval in a prescribed number of turns for each interval.
  • the temperature-sensing element 46 of Fig. 11 still has the same efficiency as the preceding embodiments.
  • Fig. 12 illustrates a temperature-sensing element 46 according to an eighth embodiment of this invention, which is formed of two band-shaped amorphous magnetic materials 48, 49 arranged is parallel at a prescribed interval to jointly constitute a pulse signal-transmitting circuit.
  • Fig. 13 shows an improved temperature-sensing element 46 according to a ninth embodiment of this invention, which comprises a band-shaped amorphous magnetic material 48 having a prescribed Curie temperature, insulation layer 56 prepared from, for example, polyethylene to cover the magnetic material 48 and conductor 52 wound about the insulation layer 56.
  • the band shaped conductive amorphous magnetic material 48 acts as a pulse signal-transmitting circuit.
  • the magnetic material 48 concurrently acting as a conductor and magnet simplifies the construction of the temperature-sensing element 46.
  • the insulation layer 56 should preferably be prepared from a material which does not melt at a lower temperature than the Curie temperature of the magnetic material 48, for example, Teflon, nylon, polyvinyl chloride, polyurethane or polyethylene.
  • Fig. 14 sets forth a temperature-sensing element 46 according to a tenth embodiment of this invention, which comprises a band-shaped magnetic material 48, insulation layer 56 coated thereon, and conductor 52 wound about the insulation layer 56 along its axis at a prescribed interval in a predetermined number of turns for each interval.
  • the temperature-sensing element 46 of Fig. 14 has the same efficiency as the preceding embodiments.
  • Fig. 15 indicates the cross section of a temperature-sensing element 46 according to an eleventh. embodiment of this invention, which comprises a band-shaped magnetic material 48, insulation layer 56 coated thereon, conductor 52 wound about the insulation layer 56 and shielding member 58 wound about the coiled conductor 52 and acting as an electrical insulation layer.
  • the temperature-sensing element 46 is reliably insulated from the other cables and is also little affected by noises.
  • Fig. 16 shows the cross section of a temperature-sensing element 46 according to a twelfth embodiment by this invention.
  • a conductive core 60 is surrounded by an insulation layer 56 in a state insulated from a band-shaped magnetic material 48.
  • the band-shaped amorphous magnetic material 48 has a relatively high resistance, then difficulties tend to be presented in processing a transmitted or reflected pulse signal. If in such case, a temperature-sensing element 46 constructed as shown in F ig. 16 is applied, then the conductive core 60 can be used as a pulse signal-transmitting circuit.
  • Fig. 17 illustrates a temperature-sensing element 46 according to a thirteenth embodiment of this invention, which comprises an insulation core member 62 prepared from, for example, synthetic resin, band-shaped amorphous magnetic material 48 wound about the core member 62, insulation layer 56 coated on the magnetic material 48, conductor 52 wound about the insulation layer 56 and shielding member 58 coated on the insulation layer 56 and acting as an electrical insulation layer.
  • the band-shaped magnetic material 48 may be wound spatially or so closely as to cause every adjacent turns to be electrically contacted by each other.
  • the band-shaped amorphous magnetic material 48 may be linearly mounted on one lateral side of the insulation core member 62.
  • Fig. 18 indicates a temperature-sensing element 46 according to a fourteenth embodiment of this invention, which is constructed by inserting a conductive core 64 made of, for example, copper, into the core member 62 of Fig. 17 which is formed of insulation material.
  • the core 64 acting as a reinforcement for the insulation core member 62 enables the band-shaped amorphous magnetic material 48 to be easily wound about the insulation core member 62.
  • the temperature-sensing element 46 of Fig. 18 has the advantage that any two of the terminals A, B, and C can be respectively used as the input and output terminals of a pulse signal. For example, where the terminals B and C are used for the above-mentioned object, then it is possible to detect the local impedance variations of the amorphous magnetic material 48 through a considerably low circuit resistance.
  • Fig. 19 indicates a temperature-sensing element 46 according to a fifteenth embodiment of the invention, which comprises an insulation core member 62 axially penetrated by a core 64, band-shaped magnetic material 48 linearly mounted on one lateral side of the insulation core member 62, insulation layer 56 coated on the core member 62 and band-shaped magnetic material 48, conductor 52 wound about the insulation layer 56 and shielding member 58 covering the wound conductor 52 and acting as an electrical insulation layer.
  • the core 64 may be omitted.
  • the temperature-sensing element of this invention is not limited to the above-mentioned embodiments.
  • the Curie temperature of the amorphous magnetic material may be properly defined in accordance with the range of a temperature to be detected.
  • the band-shaped magnetic material is not exclusively formed of an amorphous magnetic material. Any magnetic material well serves the purpose, provided it has a relatively low Curie temperature and a high relative permeability.
  • the process of winding the conductor, the turn pitch of the wound conductor or the length of the temperature-sensing element may be properly defined in accordance with the specification of a temperature variations-site detecting apparatus to be applied.
  • the temperature-sensing element may be constructed by providing a plurality of band-shaped magnetic materials.
  • a pulse signal-transmitting circuit formed of a band-shaped magnetic material and conductor jointly constituting a temperature-sensing element may be open at both ends.
  • a pulse signal is supplied to one end of a conductor or band-shaped magnetic material, and the other end is grounded through an electric resistor.
  • the relative permeability increases with temperature and sharply falls to 1 at the Curie temperature T C as seen from Fig. 20.
  • the various portions of the temperature-sensing element using such magnetic material change in relative permeability with the temperature distribution of an object on which the temperature-sensing element is mounted, even when the temperature of the magnetic material is below its specific Curie temperature. Accordingly, the characteristic impedances of the various portions of the temperature-sensing element change. When different characteristic impedances appear at the various portions of the temperature-sensing element, then pulse signals are reflected from the portions.
  • the temperature-sensing element is simultaneously supplied with pulse signals reflected from those portions of the temperature-sensing element which stand at a lower temperature than the Curie temperature, and pulse signals reflected from those portions of the temperature-sensing element reflected from those portions of the temperature-sensing element which indicate a higher temperature than the Curie temperature.
  • a temperature variation-site detecting apparatus is applied which is arranged as shown in Fig. 21, then it is possible to substantially prevent pulse signals from being reflected from those portions of the temperature-sensing element which have a lower temperature than the Curie temperature corresponding to a predetermined temperature, thereby elevating the precision with which the temperature variations of an object can be sensed.
  • a first wider U-shaped temperature-sensing element 46a and a second narrower U-shaped temperature-sensing element 46b which have about the same length, and are arranged in parallel in superposed relation ship are closely mounted on an object 30 with the narrower temperature-sensing element 46b set inside of the wider temperature-sensing element 46a, in such a manner that one arm of the wider U-shaped temperature-sensing element 46a is disposed close to the corresponding arm of the narrower U-shaped temperature-sensing element 46b.
  • the first and second temperature-sensing elements 46a, 46b may be of the same type as any of the previously described embodiments shown in Figs. 4 to 19.
  • the first temperature-sensing element 46a is formed of a band-shaped magnetic material having a Curie temperature T C1 substantially equal to the predetermined temperature T E of the object 30.
  • the second temperature-sensing element 46b is formed of a band-shaped magnetic material having a Curie temperature T C2 , for example, about 10°C higher than the aforementioned Curie temperature TCl.
  • the end X l of one arm of the first wider temperature-sensing element 46a and the end Y 1 of the other arm of the temperature-sensing element 46a are alternately connected by a switching device 66 to the output terminal of a first pulse generator 40a and a reflection preventing impedance element 68a.
  • the end X 2 of an arm of the second narrower temperature-sensing element 46b and the end Y 2 of the other arm of the temperature-sensing element 46b are also alternately connected by the switching device 66 to the output terminal of a second pulse generator 40b and a reflection preventing impeadance element 68b.
  • the switching device 66 comprises a switching contact section 70 and control section 72 for intermittently actuating the switching contact section 70.
  • the switching contact section 70 comprises, for example, four normally closed contact units Ra, Rb, Rc, Rd, and four normally open contact units Sa, Sb, Sc, Sd.
  • contact units Ra, Rb, Rc, Rd and Sa, Sb, Sc, Sd are connected in the following manner to the end X 1 of one arm of the first wider temperature-sensing element 46a and the end X 2 of one arm of the second narrower temperature-sensing element 46b, the end Y l of the other arm of the first wider temperature-sensing element 46a, and the end Y 2 of the other arm of the second narrower temperature-sensing element 46b, first and second pulse generators 40a, 40b, and impedance elements 68a, 68b.
  • the end X l of one arm of the first temperature-sensing element 46a is connected to the first contact element of the normally closed contact unit Ra.
  • the second contact element of the normally closed contact unit Ra is connected to the output terminal of the first pulse generator 40a.
  • the end X 1 of one arm of the first temperature-sensing element 46a is connected to the first contact element of the normally open contact unit Sa.
  • the second contact element of the normally open contact unit Sa is grounded through the impedance element 68a.
  • the end Y l of the other arm of the first temperature-sensing element 46a is connected to the first contact element of the normally open contact unit Sc.
  • the second contact element of the normally open contact unit Sc is connected to the output terminal of the first pulse generator 40a.
  • the end Y l of the other arm of the first temperature-sensing element 46a is connected to the first contact element of the normally closed contact unit Rc.
  • the second contact element of the normally closed contact unit Rc is grounded through the impedance element 68a.
  • the end X 2 of one arm of the second temperature-sensing element 46b is connected to the first contact element of the normally closed contact unit Rb.
  • the second contact element of the normally closed contact unit Rb is connected to the output terminal of the pulse generator 40b.
  • the end X 2 of one arm of the second temperature-sensing element 46b is connected to the first contact element of the normally open contact unit Sb.
  • the second contact element of the normally open contact unit Sb is grounded through the impedance element 68b.
  • the end Y 2 of the other arm of the second temperature-sensing element 46b is connected to the first contact element of the normally open contact unit Sd.
  • the second contact element of the normally open contact unit Sd is connected to the output terminal of the second pulse generator 40b.
  • the end Y 2 of the other arm of the second temperature-sensing element 46b is connected to the first contact element of the normally closed contact unit Rd.
  • the second contact element of the normally closed contact unit Rd is grounded through the impedance element 68b.
  • the first and second pulse generators 40a, 40b simultaneously send forth a pulse signal after a prescribed length of time has passed from the point of -time at which the operation mode of the control section 72 has been changed over.
  • the output terminal of the first pulse generator 40a is connected to one of the input terminals of a differential amplifier 74.
  • the output terminal of the second pulse generator 40b is connected to the input terminal of an amplifier 76, whose output terminal is connected to the other input terminal of the differential amplifier 74.
  • An output pulse from the second pulse generator 40b and an output pulse from the differential amplifier 74 are supplied to a pulse time difference detector 78, an output signal from which is delivered to a temperature variation site detector 80.
  • This temperation variation site detector 80 has the fundamentally same arrangement as the conventional type.
  • This temperature variation site detector 80 is supplied with a signal denoting the operation mode of the control section 72 in order to judge which of the terminals X l , X 2 of the first and second temperature-sensing elements 46a, 46b or which of the terminals Y 1 , Y 2 thereof has received a pulse signal.
  • the temperature variation site detector 80 figures out the site on an object which has an abnormal temperature from the above-mentioned judgement.
  • a tem- peracture variation-site detecting apparatus 82 is in the condition shown in Fig. 21; a magnetic material constituting the first temperature-sensing element 46a has a temperature-relative permeablity characteristic represented by curve a of Fig. 22; the Curie temperature T C1 of the magnetic material is substantially equal to a predetermined temperature T E ; a magnetic material constituting the second temperature-sensing element 46b has a temperature-relative permeability characteristic denoted by curve a of Fig. 22; and the Curie temperature T C2 of the magnetic material of the second temperature-sensing element 46b is higher than the Curie temperature T C1 of the magnetic material of the first temperature-sensing element 46a.
  • pulses relfected from the three temperature regions M l , M 2 , M 3 of Fig. 22 are sent forth from the differential amplifier 74 at the undermentioned mode.
  • the above-mentioned two kinds of magnetic material stand at a lower temperature than the predetermined level T E .
  • T E the predetermined level
  • Z 0 represents the characteristic impedance of the left side of the temperature-sensing element as viewed from point H
  • Z l denotes the characteristic impedance of the right side of the temperature-sensing element as viewed from point H
  • Vi shows the voltage of an input pulse signal.
  • a pulse signal reflected from point H has a voltage V r expressed by the following equation: As seen from Fig. 22, Z 1 > Zo results in the temperature region M 1 . A shown in Fig. 23(b), therefore, the reflected pulse signal V r is reflected with the same phase as the input pulse signal Vi.
  • the differential amplifier 74 Since the first and second temperature-sensing elements 46a, 46b are closely disposed in parallel, a pulse signal is reflected from substantially the same points on the temperature-sensing element 46a, 46b. If the amplifier 76 (Fig. 21) is chosen to have an optimum gain, then the input terminals of the differential amplifier 74 are supplied with two reflected pulse signals having the same phase and voltage level. Consequently as shown in Fig. 23(d), the differential amplifier 74 sends forth no output signal.
  • the pulse time difference detector 78 is supplied in the temperature region M l with a signal completely freed of pulse signals reflected from those sections of the temperature-sensing elements 40a, 40b where the characteristic impedance changes discontinuously.
  • the relative permeability of a magnetic material constituting the first temperature-sensing element 46a stands at 1.
  • the relative permeability of a magnetic material constituting the second temperature-sensing element 46b still has a high level.
  • a pulse signal V ra reflected from point H has the opposite phase to an input pulse signal Via as shown in Fig. 23(c).
  • the characteristic impedance Z lb of the right side of the second temperature-sensing element 46b as viewed from point H is higher than the characteristic impedance Z Ob of the left side thereof as viewed from point H (Z lb > Z 0b ). Therefore, a pulse signal V rb reflected from point H of the second temperature-sensing element 46b has the same phase as the input pulse signal Vi b as shown in Fig. 23(b).
  • the differential amplifier 74 sends forth an output pulse signal V 0 having a higher voltage level than a sum of an absolute value of the voltage of the pulse signal V ra reflected from the first temperature-sensing element 46a and an absolute value of the voltage of the pulse signal V rb , reflected from the second temperature-sensing element 46b as shown in Fig. 23(e).
  • the magnetic materials constituting the first and second temperature-sensing elements 46a, 46b have a relative permeability of 1 alike. Since the pulse signals V ra , V rb reflected from point H respectively have the opposite phase to the corresponding input signals as shown in Fig. 23(c), the differential amplifier 74 produces no output signal as shown in Fig. 23(d).
  • the differential amplifier 74 sends forth an output pulse signal V 0 corresponding to a reflected pulse signal only in the temperature region M 2 .
  • This output pulse signal V 0 is supplied to the pulse time difference detector 78, which detects a difference between a point of time at which a pulse signal is received from the first pulse generator 40a and a point of time at which the output pulse signal V 0 from the differential amplifier 74 is received.
  • first and second pulse signals from the first and second pulse generators 40a, 40b are supplied to the ends Y l , Y 2 of the other arms of the U-shaped temperature-sensing elements 46a, 46b.
  • a site of abnormal temperature is detected with the other end Y l of the first temperature-sensing element 46a taken as a reference.
  • the terminals of the first and second temperature-sensing elements 46a, 46b which are to be supplied with a pulse signal are alternately changed over by the switching device 66, then, for example, two sites A 1 , A 2 (Fig. 21) of abnormal temperature can be accurately detected, then broadening the latitude where a temperature variation site-sensing element can be applied.
  • the impedance elements 68a, 68b of Fig. 21 are not always necessary, but may be omitted.
  • the amplifier 7 6 may be omitted.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)
EP19810104858 1980-06-23 1981-06-23 Appareil pour détecter les variations locales de température d'un objet et les endroits des variations de température Expired EP0044431B1 (fr)

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
JP84902/80 1980-06-23
JP8490580A JPS5710431A (en) 1980-06-23 1980-06-23 Detecting device of position at abnormal temperature
JP84905/80 1980-06-23
JP8490280A JPS5710430A (en) 1980-06-23 1980-06-23 Device for sensing position of abnormal temperature
JP55129460A JPS592852B2 (ja) 1980-09-18 1980-09-18 異常温度位置検出装置
JP129460/80 1980-09-18
JP13284380A JPS5759128A (en) 1980-09-26 1980-09-26 Temperature detecting element
JP132843/80 1980-09-26

Publications (2)

Publication Number Publication Date
EP0044431A1 true EP0044431A1 (fr) 1982-01-27
EP0044431B1 EP0044431B1 (fr) 1986-10-22

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Application Number Title Priority Date Filing Date
EP19810104858 Expired EP0044431B1 (fr) 1980-06-23 1981-06-23 Appareil pour détecter les variations locales de température d'un objet et les endroits des variations de température

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EP (1) EP0044431B1 (fr)
DE (1) DE3175500D1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5070737A (en) * 1989-02-10 1991-12-10 National Research Development Corporation Transducer which determines a position of an object by modifying differential pulses

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2615973A (en) * 1950-04-07 1952-10-28 Samuel Scrivener Jr Temperature responsive detector system
US2926343A (en) * 1956-10-11 1960-02-23 Mc Graw Edison Co Curie point fire detector cable
US3413540A (en) * 1966-07-14 1968-11-26 Carl A. Vansant Magnetic temperature sensor
FR2292962A1 (fr) * 1974-07-10 1976-06-25 Shell Int Research Procede et dispositif pour la detection d'une variation de temperature et leur application aux citernes et canalisations

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US2615973A (en) * 1950-04-07 1952-10-28 Samuel Scrivener Jr Temperature responsive detector system
US2926343A (en) * 1956-10-11 1960-02-23 Mc Graw Edison Co Curie point fire detector cable
US3413540A (en) * 1966-07-14 1968-11-26 Carl A. Vansant Magnetic temperature sensor
FR2292962A1 (fr) * 1974-07-10 1976-06-25 Shell Int Research Procede et dispositif pour la detection d'une variation de temperature et leur application aux citernes et canalisations

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US5070737A (en) * 1989-02-10 1991-12-10 National Research Development Corporation Transducer which determines a position of an object by modifying differential pulses

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EP0044431B1 (fr) 1986-10-22

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